Evaluation of conceptual models of natural organic matter (humus) from a consideration of the chemical and biochemical processes of humification

Metal Cation Complexation with Natural Organic Matter in Aqueous Solutions: Molecular Dynamics Simulations and Potentials of Mean Force

“…Whether NOM is chemically a true macromolecular entity or a supramolecular assemblage of smaller molecular fragments held together by relatively weak non-covalent interactions (primarily electrostatic and hydrogen-bonding) is still under discussion. 2,3,[25][26][27][28] Recent experimental results strongly support the supramolecular view . [29][30][31] Modeling approaches relying only on an averaged structural and compositional 5 representation of NOM are currently successful in accurately predicting the ion binding and aggregation capabilities of NOM, as well as its other functional characteristics.…”

“…2,3,[26][27][28] The TNB model fragment used in our simulations contains three carboxylic groups, three carbonyl groups, two phenolic groups, two amine groups, and four other R-OH alcohol groups and has a total molecular weight of 753 Da. [38][39][40] The size, composition, molecular weight, degree of aromaticity, and total charge density of this model are in good agreement with available experimental characterization of NOM 26,27,29 , the results of computer assisted 3-D structure elucidation, 42 and stochastic biogeochemical modeling.…”

“…[6][7][8][9][10][11] The formation of NOM coatings is also a significant factor controlling the stability of viruses in aquatic systems 12 and the performance characteristics of inorganic and polymeric nanofiltration membranes. 13,14 Common cations such as Na + , Mg 2+ , and Ca 2+ are thought to play an important role in the supramolecular aggregation of NOM molecules into colloidal particles, 2,3,[15][16][17][18][19][20] the formation of NOM surface coatings, [10][11][12][13] and the aggregation of mineral particles. 21,22 These background cations also successfully compete for binding sites with toxic metals, thus effecting their mobility in the environment.…”

“…[1][2][3] It interacts with and changes the solubility and toxicity of trace elements in natural aqueous environments. 4,5 NOM can also easily adsorb onto mineral surfaces, forming an organic coating which significantly alters the electrostatic properties of the surface and strongly affects the transport and availability of toxic species.…”

Novel Fast Pyrolysis/Catalytic Technology for the Production of Stable Upgraded Liquids

“…The molar flow concentrations of the simulated feed, desired observed product, and modeled prediction for the product composition are listed in Table 10. [18], [19], [20], [24], [25], [26], [27] 13.2 45.6 cellulose x ↔ 3x glycolaldehyde [19], [20], [25] The solution to the objective function in KME tunes the parameters to appropriately fit the desired product composition. As discussed in previous reports, the same procedure is followed for true experimental data and corresponding microkinetic reaction network.…”